A. Yep, it happens every time. Designers often suggest using white or light pastel colors for grout, with miserable results: dirt and mold. Try applying straight bleach, leave it on for a minute or two, and scrub with a small brush. Repeat as necessary. Still no success? OK, I’m not a designer, but I am suggesting something that a designer with imagination might find an interesting idea: Take out the dirty grout and put in the blackest grout you can find. Smashing! If you put in the dark grout, seal it with a tile sealer the next day.

Q. When a contractor installed a new hot air furnace in my basement, he added coils and other parts of a whole house air conditioner. When I started it up, a lot of water appeared on the basement floor, making a rather big mess. What happened and how can that be fixed?

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A. I think the installer forgot to put in a water return line leading to the outdoors. The coils on top of the furnace are cooled by the air conditioner, allowing water vapor to condense on the coils during operation. Normally a plastic line is installed in the insulated unit that contains the coils, leading to a small pump that pumps the condensate to the outdoors. Call the contractor back and have him install such a line and pump, for free.

Q. My new concrete steps get very dirty, practically every day, and I can’t seem to keep them clean? How can I do that?

A. It’s not easy to keep things clean outdoors except with a constant vigil, especially concrete that is roughened (floated with a wood trowel) to make it nonslippery. But you can power wash the concrete to keep the steps clean. Buy a power-washing machine and all will be well if Wilmington lets you use the water. For additional protection, you can apply a clear sealer to the concrete or apply one coat of a semitransparent stain.

Q. I have some white painted or anodized aluminum tubing chairs with plastic seats and backs. Whenever I touch the tubing, white powdery stuff rubs off on my clothing. It washes off easily, but it is a real nuisance. Is there any way to stop this stuff from rubbing off?

TOM, from Holliston

A. I think that the aluminum is oxidizing, or reacting to the elements in some way as it ages. That happened to my high-quality aluminum storm windows whenever I washed them. I solved the problem by hosing down the windows heavily, but that didn’t last very long, and certainly won’t help you. Check where you bought the chairs. Or, you could try painting the aluminum. Otherwise it beats the heck out of the Handyman.

Globe Handyman on Call Peter Hotton also appears in the Sunday Real Estate section. He is available 1-6 p.m. Tuesdays to answer questions on house repair. Call 617-929-2930. Hotton (photton@globe.com) also chats online about house matters 2-3 p.m. Thursdays. Go to www.boston.com

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